Starch, being the principal component in most staple foods such as cereals and tubers, is the major food carbohydrate contributing to postprandial glycemia. Digestibility of starch is directly associated with glycemic/insulinemic response and the occurrence of glucose metabolism-related health conditions like diabetes and pre-diabetes, cardiovascular disease, and obesity. Therefore, the glycemic index (GI) or glycemic response of starch in foods is increasingly becoming an important factor for human health.
GI is a measure of the rise in blood glucose level that is triggered by consumption of a carbohydrate and relates to the blood glucose profile seen over a period of 2 hours (hr) after consumption of a starch-based or sugar-containing food. GI is typically measured as the area under the blood glucose response curve (AUC) for a given amount of available carbohydrate in a test food (usually 50 g) as compared to the same amount of a reference food (usually glucose or white bread) (Wolever et al., 1991; FAO/WHO, 1997). The higher the GI the greater the blood glucose rise. Typically, a GI of 55 or less is low while a GI of 70 or more is high. Glycemic load (GL), a term related to GI, is a measure, not only GI of a given food, but also considers the amount of carbohydrate in a certain amount (e.g., serving size) of a given food. GL is GI/100 multiplied by the available carbohydrate content of a standard amount of food in grams (i.e. carbohydrates minus fiber). GI and GL of foods consumed may relate to a number of disease and pre-disease conditions such as diabetes and pre-diabetes, cardiovascular disease, cancer, and obesity. GI and GL may also relate to energy expenditure and activity level.
From a nutritional standpoint, starch has been classified into three categories based on in vitro digestion time: rapidly digestible starch (RDS) is converted to glucose in 20 minutes (min), slowly digestible starch (SDS) between 20 and 120 min, and resistant starch (RS) undigested after 120 min (Englyst et al., 1992,1996). Foods with high proportion of RDS have a high GI value based on a correlative relationship between RDS and GI (Englyst et al., 1996). The rapid increase of blood glucose level from RDS triggers the secretion of insulin from pancreas beta-cells to promote glucose uptake by muscle and adipose tissues to maintain blood glucose homeostasis, and, if the increase in postprandial glycemia is pronounced, usually generates a hypoglycemic episode between 1 and 2 hr after consumption of RDS. A long-term fluctuation of postprandial blood glucose and insulin levels will generate high stress on the glucose homeostasis regulation system, which has been directly associated with hyperinsulinemia, insulin resistance, and incidence of Type 2 diabetes.
In contrast, SDS is that portion of starch digested slower than RDS, implying that it is digested throughout the small intestine to provide a slow and prolonged release of glucose over an extended period of time. Such a moderated and controlled release of glucose may place less stress on the blood glucose regulatory system, thereby resulting in health benefits of SDS starches not only in commonly consumed foods, but also in medical applications-foods, drugs, and dietary supplements. Such SDS foods may also provide slow and sustained energy release for athletic performance, improved activity levels (memory and mental performance), and promote increased satiety for weight management.
RS is that portion of starch not digested in the small intestine. RS is, however, digested by colonic microflora amylases, and then fermented to produce short chain fatty acids (SCFAs) (acetic, propionic, and butyric).
Evidence has shown that glycemic response is highly correlated with the amount of RDS in food products, while SDS and RS are associated with hunger satiation and benefits resulted from their effects on a cascade of metabolic consequences including the release of incretin hormones [glucagon-like peptide-1 (GLP) and glucose-dependent insulinotropic polypeptide (GLP)] and slow release of insulin. Thus, starch digestion properties have been implicated in the health problems of diabetes, obesity and cardiovascular disease. Making food products with high amount of slowly digestible starch or resistant starch is currently one of the important targets of food industry.
The importance of dietary fiber in human diet and its numerous physiological functions, as well as role in the prevention and treatment of certain diseases including cardiovascular, diabetes and obesity, and more importantly those related to colon health: inflammatory bowel disease (IBD) and colon cancer, is well recognized. “Dietary fiber is the edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine.” See: Report of the Dietary Fiber Definition Committee to the Board of Directors of AACC (American Association of Cereal Chemists) International (Jan. 10, 2001). Fiber that is consumed by individuals may include natural fiber from the foods eaten as well as fiber generated from other sources added to a given food (added fiber). Fiber has also be categorized as fermentable and non-fermentable based on the extent of its fermentation in the colon. RS starch is dietary fiber and fermentable fiber under these definitions.
Health benefits are derived from both non-fermentable fiber (among others: increased fecal bulk-affecting fecal output, dilution and increased transit time of carcinogens and toxins in the colon, increased bile salt binding there by influencing cholesterol levels in the blood, and increased digesta viscosity) and fermentable fiber (production of short chain fatty acids that most importantly prevent the growth of harmful bacteria and decrease the inflammatory response). Fiber fermentation produces short chain fatty acids (e.g., acetic, propionic, and butyric acids) that contribute to colon health by increasing blood flow, improving mineral and water absorption by maintenance of low luminal pH. Butyrate has also been shown to have a positive influence on epithelial metabolism, cell cycling, the immune response, and intestinal motility. Two aspects of fermentable fiber that have received attention are preferable production of butyrate, which has promising effects for treatment of colon disorders including irritable bowel disease and colon cancers, and slow fermentation rate so that fermentation occurs in both the proximal part of the colon, and in the distal part of the colon (where most cancer lesions are known to occur). Most fermentable fibers are very rapidly fermented in the proximal part of the colon with very little fermentation in the distal part.
In food science, probiotics are used to deliver living bacterial cells to the gut of humans (and other animals) to adjust the gut ecosystem to improve health or provide health benefits. The use of probiotics is based on the concept that there is a healthy balance of bacteria in the intestinal tracts and that dysbiosis, the disruption of that balance, can result in illness. Probioitcs, for example, are used to restore the balance of gut flora which may be disrupted by antibiotic treatment. Probioitcs commonly include strains of Lactobacillis and Bifidobacterium which are considered to be beneficial to digestive health. Prebiotics are non-digestible foods which promote the growth of such beneficial bacteria in the gut. Prebiotics include various oligosaccharides, including fructooligosaccharides, inulins, lactilol, lactosucrose, lactulose, and pyrodextrins which in some way stimulate the growth of beneficial gut bacteria.
There is a need in the art for the development of dietary fibers that preferably generate butyrate on fermentation and that are available for fermentation throughout the length of the colon (both proximal and distal). Starch-based dietary fiber offers a distinct advantage because its fermentation produces proportionally more butyrate than traditional dietary fibers. Starch-based dietary fiber can also function as a prebiotic to stimulate the growth of beneficial gut bacteria, including for example Lactobacillis and Bifidobacterum strains.
A starch-based fiber material which exhibits slow fermentation, such that fermentation occurs over the length of the colon, would be of significant interest and benefit in the food and pharmaceutical arts as a food product, food ingredient, nutritional supplement or medicament. Such a fiber material would have additional health benefits generally promoting colon health and more specifically for prevention and/or treatment of diseases of the colon. A starch-based composition which combines low glycemic index with controlled-rate of glucose release with the benefits of fermentable fiber would clearly be of significant interest and benefit as a food product, food ingredient, and nutritional supplement for use by individuals for weight control and maintenance, by those with a predisposition to diabetes (prediabetics), for diabetics and more generally by those wishing to generally maintain healthy nutrition and those wishing to maintain or improve their colonic health. Furthermore, such a starch-based composition would be useful as a prophylactic composition to prevent colon disease, or as a pharmaceutical composition or medicament for treatment of diseases of the colon.
While native starches can be an excellent source of SDS and RS, the slowly digesting property is lost during thermal food processing resulting in RDS and high GI foods. The present invention provides starch-based compositions which are useful as low GI foods, even on cooking, and which provide the benefits of a starch-based fermentable fiber.
Several patents and patent applications report means for overcoming the rapidly digesting characteristics of starch. Some report the use of native starch (U.S. Pat. No. 6,316,427; WO 2005/044284 A1) and treated starches (WO 2005044284, WO 2005058973) for creation of SDS starches. Others report the use of enzymatic modification of starches (U.S. Pat. Nos. 6,890,571 and 6,929,817, W02004066955).
Methods incorporating polysaccharides for encapsulating, coating, or encasing foods have been reported . For example, U.S. Pat. Nos. 2,517,595; 2,611,708; and 2,703,286 report the use of pectin-calcium based films for encasing foods. U.S. Pat. No. 4,192,900 describes the use of a range of starch materials and polymers for preparation of texturized starch products.
U.S. Pat. Nos. 5,360,614 and 5,536,156 report a method for controlling the release of carbohydrates by encapsulation in edible coatings which is said to provide a delayed release of the carbohydrate, thereby making them useful in diabetes and exercise programs calling for sustained energy release.
U.S. Pat. Nos. 5795606 and 5972399 report the use of a cation crosslinked polysaccharide coating to substantially reduce the glycemic response of ready-to-eat, nonfried foods made up of a cooked and hydrated carbohydrate core. The food is reported to be useful for the treatment of diabetes, hypoglycemia, and glycogen storage disease, and for suppressing appetite and assisting the performance of sustained physical activity. The invention also reports on a food preparation consisting of a coated carbohydrate core for cooking in an aqueous medium. The food preparation is described as a crosslinkable polysaccharide coated carbohydrate core that is further crosslinked during cooking of the food in a medium comprising the dissolved cation. The invention also reports to a method of preparing a food, comprising heating the indicated coated core in an aqueous medium comprising crosslinking cations. The heating is done to crosslink the crosslinkable polysaccharide and to cook and to hydrate the core. The carbohydrates reported suitable for the core may include one or more of the following: peptidoglycan, polysaccharide, oligosaccharide, disaccharide, monosaccharide and sugar alcohol. In particular, the carbohydrate may be starch, dextrin, sucrose, mannose, maltose, glucose, fructose, lactitol, xylitol, sorbitol, lactose and mannitol. Most preferably, the carbohydrate includes at least starch. Some examples of the carbohydrate-containing foods included for the core are: rice grains, pasta, breakfast cereal, and vegetables (whole, cubes, dices, slices or chips). Further, the reported core may also be a food ingredient such as a flour granule or granules, or a starch granule or granules. Such food ingredients, i.e., suitable for employment as the core of the invention, include those incorporated into puddings, candy bars, and food bars, and into instant foods such as soups and dessert mixes.
U.S. Pat. No. 6,815,436 reports granulated starch compositions for treatment and/or prevention of dysglucemia. Enzymatic degradation of starch is reported to be controlled in vivo by “minimizing the surface area available to enzymatic action.” Starch granules are described as being granulated with a substance resulting in aggregated granules being at least partially encapsulated in the substance. Suitable substances are said to be non-toxic and generally recognized as safe. Suitable substances are said to include “polymers such as gum arabicum, potassium alginate, guar gum, methyl cellulose, ethyl cellulose, liquid oils, liquid and hard fats and waxes, such as paraffin, hydrogenated cottonseed oil, beeswax and carnauba wax.” Dysglucaemia is reported to be treated by administering a predetermined amount of starch in the granulated and at least partially encapsulated form. Granulation is reported to delay enzymatic degradation of the starch into reducing sugars, such as glucose. One advantage of the reported composition is stated to be that “practically all of the starch” in the composition is converted to reducing sugars allowing the accurate control of the dose optimized for each patient. Additionally it is stated that the release rate and content of reducing sugars can be accurately controlled and adjusted to the needs of a specific patient group, specific application or medical situation. Another stated advantage of the composition is that “undigested starch is prevented from reaching the colon, where it would be digested by bacteria, resulting in the formation of gas, especially in the colon.” Preparation of starch compositions are described as “cornstarch and different excipients were dry mixed in a granulator and agglomerated with water or ethanol as granulation fluid, depending on the solubility of the granulations substance used. The dry granulate was pressed into tablets.” In Example 1, native cornstarch is said to be mixed with 10% by weight potassium alginate in a high shear mixer and water is added as granulation fluid. Granules were then said to be wet sieved through a 1 mm sieve and dried. Dried granules were then said to be sieved through a 1 mm sieve and collected on a 0.5 mm sieve. A small amount of fat was said to be added (5-20%) to the granules. The composition is said to be used in the from of the granulate or pressed tablets of granulate.
U.S. Pat. No. 7,053,066 reports a food composition/food preparation method, which uses therapeutically effective amounts of additives such as hydrophilic substances (propylene glycol alginate as an example) and pharmaceutically acceptable salts in foods, to enhance the starch cell wall membrane that slows the enzymatic hydrolysis of starch resulting in controlled release of glucose. The invention relates to a method for treating overweight patients or patients with obesity.
U.S. published patent application 2006/0127453 reports a delivery vehicle suitable for carrying probiotic and bioactive compounds for aquatic animals. The vehicle is said to protect the active components from digestion and breakdown in the stomach. The delivery vehicle is described as microparticles or macroparticles comprising one or more non-digestible polymers and an emulsifier. The polymer is said to include among others starch, hemicellulose, cellulose, silicone, poly(vinyl alcohol), poly(ethylene oxide), poly(vinylpyrrolidone), and poly(hydroxyethylmethyacrylate). Descriptions of the use of starch to prepare the delivery vehicle as microparticles refer to the use of gelatinized starch. Microparticle formation by crosslinking a mixture of certain starches, emulsifier and alginate by dropping or spraying the mixture into a solution containing calcium ion is also described. The application also contains an example for the oral delivery of insulin to diabetics using a starch, emulsifier, alginate microparticle composition.